Recently, a public line network such as the Internet has allowed a plurality of terminals to share a screen, so that an operator terminal displays the screen of the destination terminal. In such a screen sharing, the operator terminal receives screen data from the destination terminal and displays the received screen data in the shared screen display area set in itself.
In such a screen sharing, in the same way as Patent Document 1, display information is generated in accordance with an operation instruction input by a user. This display information is separated into display information in a display area of the operator terminal itself and display information in the display area of another screen sharing system by applying coordinate transformation. Then, a screen is displayed on the operator terminal itself based on the display information in a display area of the operator terminal itself, and a screen is displayed on another screen sharing system based on the display information in another screen sharing system.